Overload relay

ABSTRACT

An overload relay including a switch actuated by a metal reed which is prestressed into an initial bowed configuration and normally maintained under axial pressure, said reed snapping into a reversely-bowed configuration upon the application of a relatively small force applied intermediate the ends thereof.

United States Patent [111 3,838,369 Fogle Sept. 24, 1974 OVERLOAD RELAY 3794945 2 1974 Terracol 335/188 [75] Inventor: Fredric D. Fogle, Mendham, NJ. FOREIGN PATENTS OR APPLICATIONS [7'3] Assignee; Inc East Orange, 956,154 I950 France 200/67 DB Filed? 1973 Primary Examiner-Harold Broome [21] A l NQ; 419,632 Attorney, Agent, or FirmRudolph J. Jurick 52 U.S. Cl 335/188, 200/67 DB [57] ABSTRACT [51] Int. Cl. Hlh /20 An Overload relay n luding a s it h a tuated by a [58] Field of Search 200/67 DA, 67 DB, 153 T; metal reed which is prestressed into an initial bowed [56] References Cited UNITED STATES PATENTS 2,658,972 /1953 Brown .r 200/67 DB it ill ,il l n configuration and normally maintained under axial pressure, said reed snapping into a reversely-bowed configuration upon the application of a relatively small force applied intermediate the ends thereof.

8 Claims, lll Drawing Figures llilll II II ll OVERLOAD RELAY BACKGROUND OF THE INVENTION The invention relates to an overload relay of the class in which a set of normally-closed contacts are opened in response to an electrical overload occuring in a circuit connected to the contacts. Overload relays of various constructions are available. However, in the case of overload relays designed to operate in response to a relatively small actuating force, the prior relays are of expensive construction and, generally, must be retained in a predetermined position in order to assure proper operation thereof.

An overload relay made in accordance with this invention is particularly adapted to operate in response to a relatively small force and will function properly when mounted in any position.

SUMMARY OF THE INVENTION A metal reed, prestressed into an initial, bowed configuration, is positioned in a first arcuate channel. One end of the reed is positioned for engagement with the actuating button of a normally-open microswitch, whereby spring pressure applied to the other end of the reed causes the reed to depress the button and transfer the switch to the closed state. A small force applied to the reed causes the reed to snap into a reversely-bowed configuration and into a second arcuate channel. The second channel has a maximum depth greater than the maximum depth of the first channel, whereby the effective axial length of the reversely-bowed reed is decreased, thereby relieving the pressure on the actuating button and permitting the switch to return to the open state.

An object of this invention is the provision of a sensitive overload relay of improved construction and operation.

An object of this invention is the provision of an overload relay in which the actuating element is a metal reed.

An object of this invention is the provision of a snapaction switch having a set of contacts normally maintained in a first state by a bowed reed, said contacts being transferred to a second state when the reed snaps into a reversely-bowed configuration upon the applica tion of a force normal to reed surface.

An object of this invention is the provision of an overload relay including a bowed reed normally supported on an arcuate surface and spring-biased in the axial direction and into contact with the actuating button of a spring-biased switch, and means responsive to an electrical overload condition for applying a force against the reed surface, thereby to cause the reed to snap into a reversely-bowed configuration and relieving the pressure on said actuating button.

The above-stated and other objects and advantages of the invention will become apparent from the following description when taken with the accompanying drawings. It will be understood, however, that the drawings are for purposes of illustration and are not to be construed as defining the scope or limits of the invention, reference being had for the latter purpose to the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings wherein like reference characters denote like parts in the several views:

FIG. 1 is a diagrammatic representation, in top plan, showing the switch-actuating mechanism of an overload relay made in accordance with this invention;

FIG. 2 is a corresponding diagrammatic representation in side elevation and showing the position of the reed when the switch is in the closed position;

FIG. 3 is similar to FIG. 2, but showing the position of the reed when the switch is in the open position;

FIG. 4 is a top plan view of an overload relay made in accordance with this invention;

FIG. 5 is a side elevation view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a bottom plan view similar to FIG. 6 but with the botton half of the reed housing and the electro-mechanical actuator removed;

FIG. 8 is an enlarged isometric view of the reset rod and slider;

FIG. 9 is a cross-sectional view taken along the line IX-IX of FIG. 8;

FIG. 10 is a cross-sectional view taken along the line X-X of FIG. 4, drawn to an enlarged scale and show ing the reed in the normal, bowed configuration wherein the switch is in the closed position; and

FIG. II is similar to FIG. I0 but showing the reed in a reversely-bowed configuration, which results in the switch being set to open position.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to FIG. I, there is shown a reed 10 made of a spring material such as, for example, phosphor bronze, said reed normally being confined between a compression spring 11 and the actuating button 12 of a conventional microswitch 13. The spring maintains the reed under compression at a pressure which far exceeds the buckling point of the reed. To prevent buckling of the reed, the reed is prestressed into an initial slightly-bowed configuration, that is, the reed has a slight residual curvature to which it returns in the absence of any force applied thereto. The bowed reed rests against the bottom wall of a relatively shallow, concave channel formed in a fixed member I4, see FIG. 2, said wall having a radius of curvature corresponding substantially to that of the curved reed. In FIG. 2, the reed-supporting, arcuate surface is shown as a smooth curve, but in the actual device such surface is formed of a plurality of flat steps, as shown by the bottom wall 18 of a concave channel formed in the fixed member 19. Thus, the reed is supported at a plurality of points spaced along its axis. These reedsupporting points are close enough together so that the buckling point of each reed increment is not exceeded, the buckling point being inversely proportional to the square of the distance between adjacent reed-support points.

The actuating button 12, of the switch 13, is springbiased and normally extends a predetermined distance from the switch housing. Upon depression of the actuating button, the contacts of the switch are transferred from one to another state, thereby opening or closing an external electrical circuit connected to the switch terminals 15 and'lfi. The compression spring 11, FIG. 2, is confined between the fixed surface 17 and a slider 20. In the assembly of the device, the slider is moved to the left, manually, and the reed is positioned on the concave support surface of the fixed member 14. In the initial bowed configuration, the effective axial length of the reed is greater than the corresponding length of the fixed members 14 and 19. When the slider is released, the compressed spring 1 l presses the slider into contact with the end of the reed, said reed now being displaced toward the button 12. Before the slider reaches its limit of travel, the reed depresses the button to an extent sufficient to cause actuation of the switch. Assuming the switch is a normally-open type, the pressure exerted upon the reed end by the compressed spring 11 maintains the switch in the closed position. Now, when a relatively small force is applied momentarily to the reed surface in the direction of the arrow (a), the center portion of the reed is pushed away from its support points, whereby the compressed reed becomes unstable and snaps into the reversely-bowed configuration as shown inFIG. 3. The reed now rests against the arcuate surface formed in the fixed member 19, said arcuate surface being somewhat longer than the aligned arcuate surface formed in the fixed member 14. Consequently, the effective axial length of the reed is decreased, thereby relieving the pressure on the switch actuating button 12 and resulting in the switch contacts returning to the normal open-circuit condition. The reed remains in the position shown in FIG. 3 until the device is reset. This is done by manually moving the slider to the left to remove the spring pressure acting on the reed. The reed now snaps back into its initial bowed configuration and returns to rest against the arcuate surface formed in the member 14. Upon release of the'slider, the spring 11 causes the reed to again depress the switch-actuating button 12.

In the case of an overload relay, an overload condition in a circuit connected to the switch terminals 15 and 16 causes the energization of an electromechanical actuator which applies the force to the reed in the direction of the arrow (a), FIG. 2, thereby causing the reed to snap to the position shown in FIG. 3 and opening the circuit between the switch terminals.

Reference now is made to FIGS. 4-7 showing an overload relay made in accordance with this invention. The microswitch 13 is secured to an integral ledge portion extending from the top portion 26 of an elongated plastic housing, the bottom portion of the housing being identified by numeral 27. Extending from the top portion of the housing are a pair of integral bosses 28 and 29, each boss having a central hole extending therethrough and communicating with the interior of the housing. A reset rod 30 is slidably supported by the boss 28 and an indicator pin 31 is slidable in the hole formed in the boss 29, all for purposes which will be described hereinbelow. An electro-mechanical actuator is secured to the bottom housing portion 27, said actuator comprising spaced plates 32 and 33, vertical posts carrying the coils 34 and 35, and a reed-deflecting pin 37 which is slidable in an axial hole formed in the rod 38. All parts of this actuator are made of soft iron with the exception of the pin 37 which is made of a plastic. Visible in FIGS. 6 and 7 is the projecting end of the reed 10, which end is in engagement with the actuating button 12 of the switch 13. FIG. 7 shows the step-like, concave channel 40 formed in the top housing portion 26, which channel corresponds to the channel identified by the numeral 18 in FIGS. 2 and 3. The channel 40 has a width slightly greater than that of the reed. Also formed in the housing portion 26 are recesses 41 and 42 which accommodate the slider 43, this slider corresponding to the slider identified by the numeral 20 in FIGS. l-3. Confined between the walls of the recess 41 and the outwardly-extending arms 44, 45 of the slider, are two compressed springs 46, 47, which springs function in the same manner as the springs 11 shown in FIGS. 1-3.

The configuration of the slider 43 is shown in FIGS. 8 and 9, which figures also include the reset rod 30. The slider, made of a suitable plastic, comprises a generally-rectangular body 50, integral arms 44, 45, and an integral, upstanding tab 51. The part of the body which is proximate to the arms 44, 45, has a hollow interior of generally-square, cross-sectional configuration, and an apperture 53 is formed in the top wall 54. The other end of the body 50 has a solid interior with a sloping wall 55 extending from the apperture 53 to the bottom of the body. The reset rod 30 has a rectangular end portion 57 terminating in a sloping end wall which corresponds to the sloping wall 55. When the end portion 57, of the reset rod, is slidably inserted into the open bottom portion of the slider body, the sloping end wall of the rod engages the sloping wall of the body, whereby further movement of the rod toward the body results in a displacement of the slider to the left, as viewed in FIGS. 8 and 9.

Reference now is made to the enlarged crosssectional view of FIG. 10. The reed 10 is shown in its normal position resting upon the edges defining the steps forming the relatively shallow, concave channel 59 in the bottom housing section 27. The compressed springs, (not visible in this particular view, but see FIG. 7), press the upstanding tab 51, of the slider, against the end of the reed. In this condition of the device, the actuating button 12, of the normally-open switch 13, is depressed, whereby an external electrical circuit connected to the switch is closed. The indicator pin 31 has a head 61 which engages the reed under the action of a weak spring 62. When the reed is in the illustrated position the pin does not protrude from the boss 29. The coil 34 is connected to the electrical circuit in such manner that when an overload condition occurs in such circuit the voltage applied across the coil is sufficient to cause the armature 60 to be attracted to the iron rod 38. This drives the pin 37 upwardly, thereby causing the reed to snap into the reversely-bowed configuration as shown in FIG. 11. When this happens, the contacts of the switch 13 return to the normally-open position and a portion of the indicator pin 31 protrudes from the boss 29. Preferably, the pin has a red color to warn an observer that an overload condition exists in the circuit connected to the switch terminals.

To reset the relay, the reset rod is depressed, thereby moving the slider 43 in a direction away from the reed. When the upright tab 51, of the slider, is clear of the reed end, the reed is free of any external force and the reed thereupon snaps back to its initial curvature and returns to rest in the concave channel formed in the bottom portion of the reed housing. A release of the finger pressure on the reset rod, permits the compressed springs 46 and 47, see FIG. 7, to press the tab of the slider into engagement with the end of the reed, whereby the reed depresses the button 12 to close the switch contacts. However, if the overload condition has not been corrected, the coil 34 remains energized and the pin 37 projects into the reed housing. Under this condition, the reed cannot return to its initial position and the switch contacts cannot be transferred to the circuit-closed position even though the reset rod is depressed and released.

The electro-mechanical actuator includes two coils 34 and 35, see FIG. 5, to provide high and low-current triggering of relay. Although the invention has been described with specific reference to an overload relay having an electromechanical actuator, it is apparent that the described reed mechanism is adapted for the operation of a spring-biased switch in response to the displacement of the reed from its initial bowed configuration by suitable force. The force required for such reed displacement is of a very low order of magnitude, as the force must overcome the small reed bias force and a very small part of the end-load force on the reed caused by the concave curvature. In an actual device made as herein-described, the reed has a length of 1.250, inches, a width of 0.200 inch and a thickness of 0.004 inch, with a 0.012 inch concaveness. Such device is not subject to malfunction due to mechanical shock and will function properly in any position.

Having now described the invention what I desire to protect by letters patent is set forth in the following claims.

I claim:

1. An operating mechanism for an electrical switch having contacts controlled by a spring-biased actuator member movable between first and second positions, said mechanism comprising,

a. means forming first and second complementary, arcuate channels of substantially equal axial length, said second channel having a greater depth than the first channel,

b. a metal reed prestressed into an initial bowed configuration, said reed normally resting on the bottom of said first channel,

c. means positioning the said actuator member for engagement by one end of the reed when the actuator is in the first position,

d. means applying an axial pressure to the other end of the reed, said pressure being sufficient to cause the said one end of the reed to engage the actuator member and move it from the first to the second position, and

e. means for applying a force to the reed substantially normal to the reed axis, said force being sufficient to cause the reed to snap into a reversely-bowed configuration and into engagement with the bottom of the second arcuate channel, thereby relieving the pressure on said actuator member.

2. The invention as recited in claim 1, including means for temporarily removing the axial pressure applied to the other end of the reed.

3. The invention as recited in claim 1, wherein the bottom of the said channels are formed by a plurality of steps extending across the channels.

4. An overload relay comprising,

a. a housing,

b. first and second complementary, arcuate channels formed in said housing, said channels being of sub stantially equal length and corresponding ends of the channels communicating with the exterior of the housing,

c. a metal reed having a prestressed initial curvature and normally resting on the arcuate surface of the first channel,

d. an electric switch carried by the housing and having a spring-biased actuating button positioned for engagement by one end of the reed,

e. a slider mounted for sliding movement in said housing,

. spring means pressing the slider into engagement with the other end of the reed and causing the reed to depress said actuating button,

g. means for displacing the reed from the arcuate surface of the first channel in response to an overload condition in an external circuit connected to the said switch, said reed snapping into a reverse curvature and into engagement with the arcuate surface of said second channel and thereby relieving the pressure on the said actuating button, and

b. means for moving the said slider out of engagement with the reed, said reed now returning to its initial curvature and position of rest on the arcuate surface of the said first channel.

5. The invention as recited in claim 4, wherein the bottom walls of the said channels comprise a plurality of steps extending laterally across the channels.

6. The invention as recited in claim 4, wherein the said means for displacing the reed is an electromechanical actuator carried by the said housing and including a pin mounted for sliding movement relative to the reed surface, said pin striking the reed upon energization of the actuator.

7. The invention as recited in claim 4, including an indicator slidable in a hole formed in a wall of the housing and spring-biased into engagement with the reed, a portion of said indicator protruding from the housing when the reed is in the reverse curvature configuration.

8. The invention as recited in claim 4, wherein the said slider comprises a body having a sloping wall portion spanning a pair of parallel walls, and wherein the said means for moving the slider comprises a rod slidable in a hole formed in a wall of the housing, one end portion of the rod projecting from said housing and the other end portion of the rod having a generally rectangular configuration and slidable between the walls of the slider, the said other portion of the rod terminating in a sloping end which engages the sloping wall portion of the slider upon depression of the said rod.

l l l= 

1. An operating mechanism for an electrical switch having contacts controlled by a spring-biased actuator member movable between first and second positions, said mechanism comprising, a. means forming first and second complementary, arcuate channels of substantially equal axial length, said second channel having a greater depth than the first channel, b. a metal reed prestressed into an initial bowed configuration, said reed normally resting on thE bottom of said first channel, c. means positioning the said actuator member for engagement by one end of the reed when the actuator is in the first position, d. means applying an axial pressure to the other end of the reed, said pressure being sufficient to cause the said one end of the reed to engage the actuator member and move it from the first to the second position, and e. means for applying a force to the reed substantially normal to the reed axis, said force being sufficient to cause the reed to snap into a reversely-bowed configuration and into engagement with the bottom of the second arcuate channel, thereby relieving the pressure on said actuator member.
 2. The invention as recited in claim 1, including means for temporarily removing the axial pressure applied to the other end of the reed.
 3. The invention as recited in claim 1, wherein the bottom of the said channels are formed by a plurality of steps extending across the channels.
 4. An overload relay comprising, a. a housing, b. first and second complementary, arcuate channels formed in said housing, said channels being of substantially equal length and corresponding ends of the channels communicating with the exterior of the housing, c. a metal reed having a prestressed initial curvature and normally resting on the arcuate surface of the first channel, d. an electric switch carried by the housing and having a spring-biased actuating button positioned for engagement by one end of the reed, e. a slider mounted for sliding movement in said housing, f. spring means pressing the slider into engagement with the other end of the reed and causing the reed to depress said actuating button, g. means for displacing the reed from the arcuate surface of the first channel in response to an overload condition in an external circuit connected to the said switch, said reed snapping into a reverse curvature and into engagement with the arcuate surface of said second channel and thereby relieving the pressure on the said actuating button, and h. means for moving the said slider out of engagement with the reed, said reed now returning to its initial curvature and position of rest on the arcuate surface of the said first channel.
 5. The invention as recited in claim 4, wherein the bottom walls of the said channels comprise a plurality of steps extending laterally across the channels.
 6. The invention as recited in claim 4, wherein the said means for displacing the reed is an electro-mechanical actuator carried by the said housing and including a pin mounted for sliding movement relative to the reed surface, said pin striking the reed upon energization of the actuator.
 7. The invention as recited in claim 4, including an indicator slidable in a hole formed in a wall of the housing and spring-biased into engagement with the reed, a portion of said indicator protruding from the housing when the reed is in the reverse curvature configuration.
 8. The invention as recited in claim 4, wherein the said slider comprises a body having a sloping wall portion spanning a pair of parallel walls, and wherein the said means for moving the slider comprises a rod slidable in a hole formed in a wall of the housing, one end portion of the rod projecting from said housing and the other end portion of the rod having a generally rectangular configuration and slidable between the walls of the slider, the said other portion of the rod terminating in a sloping end which engages the sloping wall portion of the slider upon depression of the said rod. 